Monocrystalline semiconductor wafer comprising defect-reduced regions and method for producing it

ABSTRACT

Monocrystalline semiconductor wafers have defect-reduced regions, the defect-reduced regions having a density of GOI-relevant defects within the range of 0/cm 2  to 0.1/cm 2  and occupy overall an areal proportion of 10% to 100% of the planar area of the semiconductor wafer, wherein the remaining regions of the semiconductor wafer have a significantly higher defect density than the defect-reduced regions. The wafers may be produced by a method for annealing GOI relevant defects in the wafer, by irradiating defined regions of a side of the semiconductor wafer by laser wherein each location is irradiated with a power density of 1 GW/m 2  to 10 GW/m 2  for at least 25 ms, wherein the laser emits radiation of a wavelength above the absorption edge of the wafer semiconductor material and wherein the temperature of the wafer rises by less than 20 K as a result of irradiation.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority to U.S.application Ser. No. 11/828,392 filed Jul. 26, 2007, which claimspriority to German Application No. DE 10 2006 034 786.2, filed Jul. 27,2006, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a monocrystalline semiconductor wafer havingregions with a very low and homogeneous density of GOI-relevant defects.The invention also relates to a method for annealing GOI-relevantdefects in a monocrystalline semiconductor wafer, wherein at least oneside of the semiconductor wafer is irradiated by means of a laser.

2. Background Art

Semiconductor wafers, in particular silicon wafers, are generally usedfor producing microelectronic components. In the semiconductor industry,and in particular in silicon technology, which has advanced very farscientifically and also technologically, the quality requirements of thesemiconductor wafers increase further and further as time goes on, inview of the ever further decreasing smallest feature sizes of themicroelectronic components.

In order to meet these requirements, several types of very low-defectsemiconductor wafers were developed: polished semiconductor wafersproduced from extremely low-defect single crystals (e.g. EP0972094B1),thermally treated semiconductor wafers (e.g. EP0829559B1) orsemiconductor wafers having an epitaxially deposited silicon layer.

It has been found, however, that even the best semiconductor wafersknown at the present time pose problems in specific applications, suchas, for example, SOI (Silicon On Insulator), Strained Silicon or sSOI(strained Silicon On Insulator), associated with line widths (designrule)<100 nm during production or during operation of the components.Thus, leakage currents, short circuits, deviating diode characteristiccurves, hot spots, gate oxide failure or poor reliability of thecomponents lead to failure. This is described comprehensively andextensively in the literature, for example:

It is thus described that ingrown vacancy clusters lead to problems inthe reliability of the gate oxide [K. Yamabe, K. Taniguchi, Y.Matsushita, in PROC. OF THE INTERNAT. RELIABILITY PHYS. SYMP., IEEE, NJ,184 (1983)], component isolation faults [M. Muranaka, K. Makabe, M.Miura, H. Kato, S. Ide, H. Iwai, M. Kawamura, Y. Tadaki, M. Ishihara, T.Kaeriyama, JPN. J. APPL. PHYS., 37, 1240 (1998)] and faults in memorytrenches [E. Dornberger, D. Temmler, W. v. Ammon, J. ELECTROCHEMICALSOCIETY 149, G226-G231(2002)]. These problems are aggravated withincreasing structure miniaturization—particularly when the vacancyclusters reach the magnitude of typical component magnitudes such ase.g. gate lengths. Vacancy clusters lead to tiny pits in SOI structuresand to holes in very thin silicon films, and are thus “killer defects”[G. K. Keller, S. Cristoloveanu, J. APPL. PHYS. 93, 4955 (2003)].

The semiconductor wafers mentioned above can only inadequately meet thedemands imposed by future generations of components, in particular asfar as the areal and local properties of the defect homogeneity areconcerned.

SUMMARY OF THE INVENTION

An object of the invention was to provide a semiconductor wafer in whichthe problems described do not occur even upon further miniaturization ofthe components. These and other objects are achieved by means of amonocrystalline semiconductor wafer having defect-reduced regions,wherein the defect-reduced regions have a density of GOI-relevantdefects within the range of 0/cm² to 0.1/cm² and occupy overall an arealproportion of 10% to 100% of the planar area of the semiconductor wafer,wherein the remaining regions of the semiconductor wafer have asignificantly higher defect density than the defect-reduced regions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below with reference tofigures:

FIG. 1 shows GOI relevant defects in the edge region of a quadrant of asilicon wafer according to the invention that were measured with the aidof the method disclosed in DE19835616A1. The defects are represented aslight points.

FIG. 2 shows, analogously to FIG. 1, GOI-relevant defects on a quadrantof a silicon wafer that is not according to the invention.

FIG. 3 shows a schematic illustration of an embodiment of the methodaccording to the invention in which the semiconductor wafer is scannedhelically by means of the laser beam.

FIG. 4 shows defects behind the fracture edge of a silicon wafer beforeirradiation by means of a laser.

FIG. 5 shows the same fracture edge as FIG. 4, but after briefirradiation by means of a laser.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The term “GOI relevant” defects denotes all defects which adverselyaffect the quality of a gate oxide produced at the correspondinglocation. The density of the GOI relevant defects is preferably measuredwith the aid of the method of IR-Lock-In thermography disclosed inDE19835616A1, since this method enables large-area detection ofprecisely those defects which cause GOI defects. Thus, in contrast toconventional GOI tests, even very low defect densities of 0.1/cm², forexample, can be determined quantitatively.

By contrast, other detection methods such as e.g. laser scanning methodsby which the entire wafer surface is examined for defects aresignificantly less well suited since although the defects detected bysaid methods can lead to a failure of a component, they need notnecessarily lead to such failure. Defects that have no influence on theGOI-quality, such as e.g. particles adhering to the surface, are alsodetected. On the other hand, in the production of microelectroniccomponents, not only the surface of the semiconductor wafer but also acertain layer below the surface is utilized. This means that detectionmethods which only examine the wafer surface or a depth perpendicular tothe surface that is inadequate for the later component cannot, inprinciple, find all GOI-relevant defects.

GOI-relevant defects are, for example, vacancy clusters (“crystaloriginated particles”, COPs or Voids) or oxygen precipitates (alsocalled “bulk micro defects”, BMDs).

According to the invention, the defect-reduced regions of thesemiconductor wafer occupy a proportion of 10% to 100% of the planararea of the semiconductor wafer. The term planar area denotes the entireregion of the substantially parallel areas of at least one side of thesemiconductor wafer. Said region is utilized maximally for theproduction of microelectronic components. By contrast, the planar areadoes not include a beveling or rounding generally present at the edge,i.e. in the circumferential region of the semiconductor wafer.

The defect-reduced regions have a very low and preferably extremelyhomogeneous density of GOI-relevant defects. Preferably, the density ofthe GOI relevant defects deviates at arbitrary locations within thedefect-reduced regions by at most 10% from the average value of thedensity of GOI relevant defects that is determined in the defect-reducedregions. The remaining regions of the semiconductor wafer have asignificantly higher defect density than the defect-reduced regions.Preferably, the density of GOI relevant defects in the remaining regionsis at least twice as great as in the defect-reduced regions.

The defect-reduced regions according to the invention preferably have adefined lateral extent, i.e. a defined extent parallel to the surface ofthe semiconductor wafer. This is manifested by the fact that the densityof the GOI relevant defects changes abruptly at the boundaries betweenthe defect-reduced regions and the remaining regions of thesemiconductor wafer. Preferably, the density of GOI relevant defectschanges by at least a factor of 2 at the boundaries between thedefect-reduced regions and the remaining regions along a section havinga length of 0.5 mm that runs parallel to the planar areas of thesemiconductor wafer and perpendicular to the respective boundary betweenthe defect-reduced region and the non-defect-reduced region. In contrastto semiconductor wafers in accordance with the prior art which likewisehave regions having a relatively low density of GOI relevant defects andother regions having a relatively high density of GOI relevant defects,these different regions in a semiconductor wafer according to theinvention do not merge fluidly into one another, but rather are sharplydemarcated from one another.

Defect-optimized silicon in accordance with the prior art has a highdensity of very small defects having a diameter of less than 30 nm. Thesemiconductor wafers according to the invention also have a very lowdensity of these small defects. In contrast to the prior art, however,the semiconductor wafers according to the invention achieve a density ofGOI relevant defects of down to 0/cm².

Preferably, the defect-reduced regions extend over the entire thicknessof the semiconductor wafer. They therefore differ significantly in thisfeature, too, from the conventional low-defect layers at the surface ofsemiconductor wafers which are produced for example by suitable thermalor epitaxial methods. The depth of these known low-defect layers isgenerally only a few micrometers.

In accordance with one preferred embodiment of the invention, thedefect-reduced regions occupy substantially the entire planar area ofthe semiconductor wafer. This should be understood to mean preferably anarea proportion of 95% to less than 100% or even to 100% of the planararea of the semiconductor wafer. The advantages of this embodiment arethe homogeneity that can be achieved, a higher yield in chip production,maximum area utilization and simple production and process sequences.

One example of this embodiment is illustrated in FIG. 1. TheGOI-relevant defects were measured with the aid of the method disclosedin DE19835616A1. The entire planar area of the represented quadrant ofthe silicon wafer 3 according to the invention is dark, i.e. virtuallyfree of defects. It is only in the beveled edge region 6, i.e. outsidethe planar area, that a relatively high defect density can be discernedat the multiplicity of light points. In comparison with this, FIG. 2illustrates a silicon wafer in accordance with the prior art measured bythe same method. In the case of this wafer, a relatively high density ofGOI relevant defects can be discerned on the entire planar area.

In accordance with another preferred embodiment of the invention, thedefect-reduced regions occupy only part of the planar area of thesemiconductor wafer, preferably an area proportion of 10% to 95% of theplanar area.

Preferably, the defect-reduced regions coincide with the regions on thesemiconductor wafer in which a high GOI quality is important. These areregions in which components such as transistors and memory devices, forexample, are produced.

In accordance with this embodiment, the remaining, non-defect-reducedregions are situated at locations at which a high GOI quality is not ofimportance since no gate oxide is produced in these regions. This is thecase for example along the lines at which the semiconductor wafer is cutapart (“dicing”) after production of the components and, if appropriate,thinning back (e.g. grinding back), in order to separate the individualmicrochips from one another. GOI-relevant defects are non-critical alsoat the locations at which interconnects are applied to the semiconductorwafer.

Further regions in which the GOI quality is unimportant are, forexample, test regions (apart from for a GOI test), contact regions orregions which carry a wafer identifier or are provided for theapplication of serial chip numbers or alignment marks.

This means that the position of the defect-reduced regions is defined bythe arrangement of the microelectronic components that are producedlater on the semiconductor wafer. In this embodiment of the invention,the intended later arrangement of the relevant components must alreadybe known at the time of producing the semiconductor wafer according tothe invention.

This embodiment of the invention has two significant advantages:firstly, the density of the GOI relevant defects has be reduced only onpart of the area of the semiconductor wafer, which increases theeconomic viability of production. Secondly, the GOI relevant defects, inparticular the BMDs (Bulk Micro Defects), act as gettering centers, thatis to say that they bind metallic impurities with which thesemiconductor wafer is inevitably contaminated during the production ofthe components and which alter the conduction characteristic of thesemiconductor material in an uncontrolled and undesirable manner. Thepresence of BMDs in regions in which a high GOI quality is not requiredis therefore desirable. Consequently, both an extremely low andhomogeneous density of the GOI relevant defects in the critical regionsand good gettering capability are ensured in this embodiment.

The semiconductor wafer may comprise any desired semiconductor material,but it preferably comprises substantially, that is to say at least 80%,silicon. The semiconductor wafer can also comprise substantially puresilicon to which only the customary dopants are added.

The semiconductor wafer according to the invention can be produced bysuitable irradiation of a semiconductor wafer by means of laser.

The invention therefore also relates to a method for annealing GOIrelevant defects in a monocrystalline semiconductor wafer, whereindefined regions of at least one side of the semiconductor wafer areirradiated by means of a laser, wherein each location within the definedregions is irradiated with a power density of 1 GW/m² to 10 GW/m² for aduration of at least 25 ms, wherein the laser emits radiation having awavelength lying above the absorption edge of the semiconductor materialof which the semiconductor wafer is composed, and wherein thetemperature of the semiconductor wafer rises by less than 20 K as aresult of the irradiation by means of the laser.

Methods for treating semiconductor materials by means of laser radiationare known in the prior art. By way of example, DD249998A1 discloses theirradiation of a silicon wafer by means of a light source, for example alaser, wherein the light source is to be chosen, however, such that itemits a high proportion of wavelengths below the absorption edge ofsilicon, in order that the radiation is absorbed by the silicon waferand the wafer is thereby heated in order to produce getterable defects.EP68094A2 discloses a method in which a wafer that has already beenpatterned in the context of component production is locally irradiatedby means of a laser in order to recrystallize polycrystalline siliconregions by local melting of said regions. For this purpose, it isnecessary to use a laser whose radiation is absorbed by silicon, that isto say which emits light having a wavelength below the absorption edgeof silicon. A frequency-doubled Nd:YAG-laser having a wavelength of 532nm is used, for example. U.S. Pat. No. 6,743,689B1 discloses a similarmethod, in which an already patterned semiconductor wafer is irradiatedlocally by means of a laser in the course of component production inorder to crystallize amorphous regions by increasing the temperature to1200 to 1300° C.

All these known methods pursue the aim of greatly increasing thetemperature of the semiconductor wafer locally through absorption of thelaser radiation in order to achieve certain effects.

By contrast, the method according to the invention operates at awavelength lying above the absorption edge of the semiconductormaterial. By way of example, the absorption edge of silicon is at 1.1eV, corresponding to a wavelength of approximately 1050 nm. Thesemiconductor material is therefore substantially transparent to saidradiation, the latter being absorbed by the semiconductor material onlyto a small extent. For this reason, the temperature of the semiconductorwafer rises by less than 20 K, preferably even by less than 6 K, as aresult of the irradiation by means of the laser. The term “temperatureof the semiconductor wafer” means the average, i.e. global, temperatureof the semiconductor wafer. The temperature of the semiconductor waferis preferably kept within the range of 20° C. to 50° C. during theirradiation by means of the laser. It is only at the currentlyirradiated location of the semiconductor wafer that the localtemperature can reach significantly higher values, but it preferablydoes not rise above 800° C.

Nevertheless, defects present in the semiconductor wafer cansurprisingly be annealed by the irradiation according to the inventionwithout appreciably increasing the temperature of the semiconductorwafer. By way of example, COP defects and BMD defects in monocrystallinesilicon wafers, which are unavoidable in most crystal pulling processes,can be resolved by the irradiation according to the invention.

The mode of action of the method according to the invention can beexplained as follows: although the semiconductor material itself absorbslittle radiation, the temperature of the currently irradiated volume ofthe semiconductor wafer does not rise above 800° C. (which isinsufficient for the annealing of defects) and the global temperature ofthe wafer remains virtually unchanged, an interaction between thedefects and the radiation does indeed take place. Calculations show thattemperature increases by a few 10,000 K that are locally delimited tothe defect are possible as long as the defect has optical propertiesthat differ from the surrounding silicon. Such properties are based onregions having different light refraction and surfaces of cavities inthe semiconductor material. As soon as the defect is resolved, forexample in the case of a COP by diffusion of vacancies from the COP intothe crystal lattice or in the case of a BMD by diffusion of oxygen fromthe BMD into the crystal lattice (the oxygen being present asinterstitial oxygen), the defect no longer effects scattering. Radiationenergy is not absorbed any further and the locally greatly heatedlocation immediately emits its thermal energy to the cold surroundingsemiconductor material. As a result of the temperature equalization thattakes place immediately, the temperature in the region of the formerdefect falls to the initial value so rapidly that the vacancies cannotreaggregate to form a new COP or the oxygen cannot reaggregate to form anew BMD.

The method according to the invention makes it possible to produce asemiconductor wafer according to the invention with a very low andhomogeneous density of GOI relevant defects since every location of thesemiconductor wafer which lies in one of the desired defect-reducedregions can be treated under absolutely identical conditions.

This is not possible with the methods of the prior art. Such methodsprovide, for example, particular conditions during the production of thesingle crystal (e.g. by crystal pulling according to Czochralski) inorder to suppress formation of defects to the greatest possible extent.Local influencing cannot be effected with CZ methods because radiallysymmetrical property distributions are always established. Anotherpossibility in accordance with the prior art, consists in subjecting amonocrystalline semiconductor wafer having GOI-relevant defects in aspecific size distribution and density to a thermal treatment in orderto anneal the defects, at least in a layer near the surface.Inhomogeneities of the raw material cannot be completely compensatedfor, even by a homogeneous temperature treatment. Moreover, the knownmethods do not enable the properties of the semiconductor wafer to beinfluenced locally, because in the development of the methods particularattention was always paid to processing entire semiconductor wafers inthe shortest possible time.

In the case of thermally treated semiconductor wafers, a very low-defectlayer (so-called “denuded zone”) arises at the surface, while defectscan still be detected in the depth of the semiconductor wafer. Bycontrast, through application of the method according to the invention,a reduction of defects is achieved over the entire thickness of thesemiconductor wafer.

Since the semiconductor wafer is not heated globally in the methodaccording to the invention, further advantages are afforded over themethods of the prior art:

The thermal budget of the semiconductor wafer is not increased by thetreatment according to the invention. This means that no nucleation andno diffusion take place in the solid and, consequently, other types ofdefects cannot arise or grow. Since no contamination occurs at thesurfaces, the charge carrier lifetime remains virtually unchanged.

Practically no diffusion processes take place in the globally coldsemiconductor wafer. Dopant concentrations set during the production ofthe single crystal are therefore maintained unchanged.

The mechanical properties of the semiconductor wafer are altered neithertemporarily nor permanently by the inventive treatment. For larger waferdiameters, such as 200 mm or higher (e.g. 300 mm and 450 mm waferdiameters), increasing point loadings are produced in the supports forthermal processes. In contrast to this, in the method of the invention,there is no risk of plastic deformation of the semiconductor wafer thatleads to damage to the crystal lattice, in particular to slip.Generally, slip cannot propagate in the cold semiconductor material.Thermal gradients are locally delimited to the regions in the laser beamand around the defects. Consequently, no global thermal stresses occurin the semiconductor wafer. This significantly reduces the risk offracture of the semiconductor wafer during and after the treatment.

The method is generally applied to substantially round, unpatternedsemiconductor wafers. Preferably, the starting material chosen should bea semiconductor wafer having defects which on average have a diameter ofless than 70 nm, since small defects are resolved more rapidly and thetime expended on the method is thereby reduced. Semiconductor wafershaving an average defect diameter of more than 70 nm can likewise befreed of the GOI-relevant defects by the inventive method, but longerirradiation times should be chosen.

The particular parameters of the laser irradiation depend on theproperties of the semiconductor material. Since silicon is currently themost important semiconductor material, concrete parameters are describedfor silicon, but the application of the method according to theinvention is not restricted to silicon.

In the case of silicon, lasers which emit light having a wavelength of 1μm to 7 μm are suitable, for example 1.060 μm (InGaAsP diode laser),1.064 μm (Nd:YAG laser), 2.127 μm (Ho:YAG laser), 2.940 μm (Er:YAGlaser).

The wavelengths 1.064 μm and 4.25 μm, are particularly preferred sincethere is particularly low absorption of light of these wavelengths insilicon.

In the case of silicon, the power density of the laser beam lies withinthe range of 1 GW/m² to 10 GW/m². The laser beam is preferably set to anon-divergent beam having a diameter of 3 μm to 10 μm.

The absorption of energy (in W) is proportional to the cross section ofthe defect, that is to say to the square of its radius, while the volumeof the defect is proportional to the cube of the defect radius. In orderto fill the defect with melt, an energy dependent on the volume isrequired. The cross section is the light-capturing quantity.

The energy density therefore limits the size of the defects which can beannealed. It is not possible to set an arbitrarily high energy densitysince the semiconductor wafer melts and the surface quality isdestroyed. If an even higher energy density were applied, thesemiconductor wafer would be cut by the laser beam, which isundesirable.

FIG. 4 shows frontally a fracture edge of a conventional defect-reducedsilicon wafer which was examined for defects using the measuring device“Bulk Micro Defect Analyzer MO-441” (from Mitsui Mining and Smelting,Japan). To prepare the sample, a silicon wafer was fractured along apreferred direction of the crystal lattice perpendicular to its planarsurfaces. During the measurement, individual defects lying in a range of20 to 30 μm behind the fracture edge are detected and their position isvisualized. A total of 26 defects can be discerned as dark points. Theregions of the silicon wafer adjoining the fracture edge weresubsequently irradiated by means of a laser for a very short time. FIG.5 shows the same silicon wafer after this treatment. Of the 26 originaldefects present, four defects are no longer detectable. These areidentified by arrows in FIGS. 4 and 5. To resolve all of the defects,including the large defects, a longer irradiation duration is necessary.

A semiconductor wafer has by its nature a high density ofnon-agglomerated point defects (in particular vacancies and interstitialoxygen). The point defects can be outdiffused from the semiconductorwafer (in the case of oxygen) or be recombined with interstitial silicon(in the case of vacancies) by means of a subsequent thermal treatment ifthis is necessary or advantageous for the envisaged use of thesemiconductor wafer. If the free vacancies formed by the resolution ofthe COPs are to be eliminated, the silicon wafer, after application ofthe method according to the invention, is subjected to a thermaltreatment that is suitable for injecting interstitial silicon atomswhich can recombine with the vacancies.

In the preferred embodiment of the inventive method as illustrated inFIG. 3, the entire surface of the semiconductor wafer 3 is scanned bymeans of a laser 1. The simultaneous use of a plurality of lasers isalso possible. The material of the semiconductor wafer is largelytransparent to the laser beam 2. The laser beam 2 has a defined crosssection. In order to treat the entire area of the semiconductor wafer 3,the semiconductor wafer can be rotated (4) about its axis. At the sametime, the relative position of laser 1 and semiconductor wafer 3 isslowly shifted in the radial direction (5). This is preferably done insuch a way that the region in which the laser beam 2 impinges on thesemiconductor wafer 3 moves by not more than one beam diameter in theradial direction after one rotation. A whole-area treatment can also beachieved in a similar manner by scanning the semiconductor wafer line byline. In this case, the rotation 4 of the semiconductor wafer 3 shouldbe replaced by a second linear movement, preferably directedperpendicular to the movement 5.

Edge regions of the semiconductor wafer can be excluded from theirradiation during the scanning. Regions that are not intended to beconverted into defect-reduced regions can likewise be excluded. Sincethe irradiation takes place locally, it is possible to produce bothhomogeneous and in targeted fashion inhomogeneous properties of thedefect distribution. In any case the relative movement between laser andsemiconductor wafer is controlled such that every location within aregion that is intended to be converted into a defect-reduced region isirradiated at least for 25 ms.

In a further embodiment, the defect distribution on the semiconductorwafer is measured prior to the laser treatment and the parameters of thelaser treatment are adapted to the local defect sizes, etc. This alsoimproves the throughput and hence the economic viability of the method.

Further preferred embodiments of the method according to the inventionresult from adaptation to the properties of the semiconductor waferbefore the treatment according to the invention and also to the desiredproperties after said treatment. In particular the power density of thelaser beam and the required duration of the irradiation are defined bythe type and size of the defects to be resolved.

By way of example, an irradiation duration of more than 25 ms and apower density of the laser beam of between 5 and 10 GW/m² are used inorder to resolve COPs having a diameter of less than 90 nm in a siliconwafer.

An irradiation duration of more than 25 ms and a power density of thelaser beam of between 7.5 and 10 GW/m² are employed in order to destroythe oxide layer on the inner wall of COPs having a diameter of less than1250 nm. COPs having an oxide layer and a diameter of less than 90 nmcan be completely resolved under these conditions.

A power density of more than 1 GW/m² and an exposure time of more than25 ms can be used for resolving BMDs.

The method of the invention is able to produce all semiconductor wafersof the invention in accordance with the claims, but is not restrictedthereto.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A monocrystalline semiconductor wafer having defect-reduced regions,wherein said defect-reduced regions have a density of GOI-relevantdefects within the range of 0/cm² to 0.1/cm² and occupy overall an areaproportion of 10% to 100% of the planar area of the semiconductor wafer,wherein remaining regions of the semiconductor wafer have asignificantly higher defect density than the defect-reduced regions. 2.The monocrystalline semiconductor wafer of claim 1, wherein the densityof the GOI relevant defects in the remaining regions is at least twiceas great as in the defect-reduced regions.
 3. The monocrystallinesemiconductor wafer of claim 1, wherein the density of the GOI relevantdefects deviates at arbitrary locations within the defect-reducedregions by at most 10% from the average value of the density of the GOIrelevant defects that is determined in the defect-reduced regions. 4.The monocrystalline semiconductor wafer of claim 1, wherein thedefect-reduced regions extend over the entire thickness of thesemiconductor wafer.
 5. The monocrystalline semiconductor wafer of claim3, wherein the defect-reduced regions extend over the entire thicknessof the semiconductor wafer.
 6. The monocrystalline semiconductor waferof claim 1, wherein the defect-reduced regions occupy an area proportionof 95% to 100% of the planar area of the semiconductor wafer.
 7. Themonocrystalline semiconductor wafer of claim 3, wherein thedefect-reduced regions occupy an area proportion of 95% to 100% of theplanar area of the semiconductor wafer.
 8. The monocrystallinesemiconductor wafer of claim 4, wherein the defect-reduced regionsoccupy an area proportion of 95% to 100% of the planar area of thesemiconductor wafer.
 9. The monocrystalline semiconductor wafer asclaimed claim 1, wherein the defect-reduced regions occupy an areaproportion of 10% to 95% of the planar area of the semiconductor wafer.10. The monocrystalline semiconductor wafer of claim 1, wherein thedensity of the GOI relevant defects changes abruptly at the boundariesbetween the defect-reduced regions and the remaining regions of thesemiconductor wafer.
 11. The monocrystalline semiconductor wafer ofclaim 10, wherein the density of the GOI relevant defects changes by atleast a factor of 2 at the boundaries between the defect-reduced regionsand the remaining regions along a section having a length of 0.5 mm thatruns parallel to the planar areas of the semiconductor wafer andperpendicular to the respective boundary.
 12. The monocrystallinesemiconductor wafer of claim 1, which comprises at least 80% silicon.13. The monocrystalline semiconductor wafer of claim 5, wherein thedefect-reduced regions occupy an areal proportion of 95% to less than100% of the planar area of the semiconductor wafer.